1. Field of the Invention
The present invention pertains to apparatus for dispensing flowable materials such as liquids.
2. Description of the Related Art
Products made by blending a number of flowable components frequently offer manufacturing advantages over other techniques. For example, in the paint industry, various colors of paint or other coatings are routinely mixed on an as-needed basis. The advantages of these types of distribution systems is becoming well-known and has revolutionized retail sales of paints and other coatings, where custom-mixed coatings are provided on demand for walk-in-customers. Custom blending or tinting of a paint usually requires adding carefully measured quantities of different coloring agents to a paint base. Typically, the tinting materials are dispensed directly into a container of paint base, sequentially, one at a time.
High volume operations, particularly those on an industrial scale, have required faster mixing operations and attention has been paid to speeding up sequential dispensing systems. However, it has also been recognized that alternative types of dispensing systems, most notably simultaneous dispense systems are inherently faster than sequential dispense systems since all or at least a significant number of components are dispensed at one time, simultaneously. One example of a simultaneous dispense machine is described in PCT Published Application No. W087/05697. Pump pistons are mounted between a pair of generally circular plates. A bottom plate is movable and motor driven so as to compress and expand the pump members. Rotary valves are located on top of the pump pistons and are connected to dispense metered amounts of the pump output.
U.S. Pat. No. 4,946,100 describes a second example of a simultaneous dispense machine, wherein a motor-driven screw shaft reciprocates a ball screw back and forth along the shaft axis. An actuating arm carried on the ball screw drives a piston rod to pressurize a hydraulic circuit, which in turn drives a plurality of piston pumps mounted on a part circular base plate, directing pressurized flow to a dispense head.